dry-season-fish-populations-in-shire-valley-game-reserve-1976

Study Extent

Majete Game Reserve Wamkulumadzi river: width 2-7m and average depth of 0.3 Junction Shire River and Wankulumadzi River: width of Wankulumadzi up to 30m. Backwater of Shire River, sandy bottom 2-3m wide and up to 1m deep. Above Kapichira Falls: rock pool, sandy bottom, overhanging rocks, strong current in places. Depth up to 2m. Lengwe National Park Prior to the sinking of the two boreholes to provide permanent water supplies for the large Nyala population which is the main attraction in this park, there was no permanent water in Lengwe. Although the waterholes had been in existence since 1966 and 1970, no fish were present in either pool. Neither waterhole is connected with any stream system from which colonisation might be expected to occur. The waterholes were very shallow and saline making it difficult for vulnerable fish eggs and larval to survive. Mwabvi Game Reserve The electrofishing equipment was used to sample three pools in the bed of the Thangadzi River, one in gorge in the bed of the Mwabvi River and one isolated waterhole, Njule. During the rainy season the Mwabvi river flows into Thangadzi River which later joins Shire River.Two habitat which were inaccessible to the electrofishing apparatus were sampled with hands and a dip net. There were a pool in the bed of the Mwabvi river upstream of the gorge and a small spring in the bed of the Dande river, which flows into the Thangadzi river near the junction with the Shire River during the wet season.

Sampling

The cathode remained completely immersed in water while the handheld anode was controlled by the operator. On the immersion of the anode to complete the circuit, fish in a 1-2m radius were attracted to it, stunned and collected with a deep net. When the electric field was broken by the removal of the anode from the water stunned fish remained in the water recovered rapidly and swam away unharmed. The fish from each sampling site were sorted into species, counted and weighed. Fish of unknown species were retained for identification later. Small numbers of fish from each sampling site were retained to examine stomach contents and sexual condition, the reminder being returned to the water alive. The electrical conductivity of the water was measured at each site. This gives an indication of the amount of dissolved salts present, an important consideration since the efficiency of electrofishing depends upon the conductivity of the water. Electrofishing is inefficient in streams such as those on Zomba plateau where conductivities as low as 7uS/cm occur, but is very efficient in the saline waters of Lake Chilwa where conductivities of 16,000uS/cm were recorded in 1968, just before the lake dried up. The conductivity of Lake Malawi is 220uS/cm and of the Shire River was between 230 and 240uS/cm.

Method steps

1. The fish populations of the three reserves were considered separately and then compared later on.The common English and Chichewa names of fish were given in brackets after the scientific names when these were first mentioned in the text. A list of publications dealing with fishes of Malawi were given in the bibliography.

The resource has all the dry season fish identified to order, family and genus

1. Oreochromis
   rank: genus
2. Anguilla
   rank: genus
3. Clarias
   rank: genus
4. Chiloglanis
   rank: genus
5. Labeo
   rank: genus
6. Opsaridium
   rank: genus
7. Labeo
   rank: genus
8. Amphilius
   rank: genus
9. Astatotilapia
   rank: genus
10. Oreochromis
    rank: genus
11. Barbus
    rank: genus
12. Protomelas
    rank: genus
13. Enteromius
    rank: genus

The sample water sources where basically in the southern region of Malawi